This invention is generally directed to an overcoated photoreceptor device, and more specifically, a gold hole injecting electrode, for use in a layered photoreceptor device, and a method of imaging utilizing such device.
The formation and development of images on the imaging surfaces of photoconductive materials by electrostatic means is well known, one of the most widely used processes being xerography, as described for example in U.S. Pat. No. 2,297,691. Numerous types of photoreceptors can be employed in such systems including organic, as well as inorganic photoreceptor materials and mixtures thereof.
There are known photoreceptors wherein the charge carrier generation and charge carrier transport functions are accomplished by discrete contiguous layers. Further known are photoreceptors which include an overcoated layer of an electrically insulating polymeric material, and in conjunction with this overcoated type photoreceptor there has been proposed a number of imaging methods. However, the art of xerography continues to advance and more stringent demands need to be met by the copying apparatus in order to increase performance standards, to obtain high quality images, and to act as protection for the photoreceptor.
In one known process using overcoated photoreceptor devices there is employed a non-ambipolar photoconductor, wherein charge carriers are injected from the substrate electrode into the photoconductor surface. In such a system in order to obtain high quality images, the injecting electrode must satisfy the requirements that it injects carriers efficiently and uniformly into the photoreceptor. A method for utilizing organic overcoated photoreceptor devices has been recently discovered, and is described in copending application, U.S. Ser. No. 881,262, filed Feb. 24, 1978 on Electrophotographic Imaging Method, Simpei Tutihasi, inventor. In the method described in this application there is utilized an imaging member comprising a substrate, a layer of charge carrier injecting electrode, a layer of charge carrier transport material, a layer of a photoconductive charge generating material, and an electrically insulating overcoating layer. In one embodiment of operation the member is charged a first time with electrostatic charges of a first polarity, charged a second time with electrostatic charges of a polarity opposite to the first polarity in order to substantially neutralize the charges residing on the electrically insulating surface of the member, followed by exposing to an imagewise pattern of activating electromagnetic radiation, whereby an electrostatic latent image is formed. The electrostatic latent image may then be developed to form a visible image which can be transferred to a receiving member. Subsequently the imaging member may be reused to form additional reproductions after the erasure and cleaning steps have been accomplished. The actual operation of this member is best illustrated by referring to the Figures which are part of the present application, namely 2A to 2C.
There continues however to be a need for overcoated photoreceptors particularly inorganic overcoated photoreceptors, which have an efficient injecting electrode that not only injects holes into a transport layer on its surface at a controlled rate over a long period of time, but which electrode can also be easily fabricated.